This invention relates to heat treatment of rotationally symmetrical workpieces by induction heating.
It is known to heat treat workpieces by passing them in abutting relationship through the treatment region of an elongate induction heating apparatus or furnace where the workpieces become heated by means of the eddy currents induced in them. However, induced eddy currents themselves act to modify the original flux distribution in the treatment region of the apparatus, and the effect of the abutting workpieces within this treatment region is to modify the original flux distribution to such an extent that most of the induced currents are confined to the outer regions of the workpieces, thus giving rise to a very non-uniform heating pattern within the workpieces.
For these reasons, the usual practice has been to rely on thermal conduction for the heat to diffuse through the workpiece to enable a uniform temperature to be reached. This takes time and leads to slow and inefficient operation.